Using a water-immiscible ionic liquid to improve asymmetric reduction of 4-(trimethylsilyl)-3-butyn-2-one catalyzed by immobilized Candida parapsilosis CCTCC M203011 cells

Abstract

BackgroundWhole cells are usually employed for biocatalytic reduction reactions to ensure efficient coenzyme regeneration and to avoid problems with enzyme purification and stability. The efficiency of whole cell-catalyzed bioreduction is frequently restricted by pronounced toxicity of substrate and/or product to the microbial cells and in many instances the use of two-phase reaction systems can solve such problems. Therefore, we developed new, biphasic reaction systems with biocompatible water-immiscible ionic liquids (ILs) as alternatives to conventional organic solvents, in order to improve the asymmetric reduction of 4-(trimethylsilyl)-3-butyn-2-one (TMSB) to (S)-4-(trimethylsilyl)-3-butyn-2-ol {(S)-TMSBOL}, a key intermediate for synthesis of 5-lipoxygenase inhibitors, using immobilized Candida parapsilosis CCTCC M203011 cells as the biocatalyst.ResultsVarious ILs exerted significant but different effects on the bioreduction. Of all the tested water-immiscible ILs, the best results were observed with 1-butyl-3-methylimidazolium hexafluorophosphate (C4MIM·PF6), which exhibited not only good biocompatibility with the cells but also excellent solvent properties for the toxic substrate and product, thus markedly improving the efficiency of the bioreduction and the operational stability of the cells as compared to the IL-free aqueous system. 2-Propanol was shown to be the most suitable co-substrate for coenzyme regeneration, and it was found that the optimum volume ratio of buffer to C4MIM·PF6, substrate concentration, buffer pH, 2-propanol concentration and reaction temperature were 4/1 (v/v), 24 mM, 5.5, 130 mM and 30°C, respectively. Under these optimized conditions, the maximum yield and the product e.e. wer 97.7% and >99%, respectively, which are much higher than the corresponding values previously reported. The efficient whole-cell biocatalytic process was shown to be feasible on a 250-mL scale.ConclusionThe whole cell-catalyzed asymmetric reduction of TMSB to (S)-TMSBOL can be substantially improved by using a C4MIM·PF6/buffer biphasic system instead of a single-phase aqueous system and the resulting biocatalytic process appears to be effective and competitive on a preparative scale.

Efficient Asymmetric Reduction of 4-(Trimethylsilyl)-3-Butyn-2-One by Candida parapsilosis Cells in an Ionic Liquid-Containing System

“…Accordingly, the reaction time was greatly shortened from about 12 h to 1 h when replaced the IL/buffer biphasic system to the C 2 OHMIM·NO 3 -containing co-solvent system. Moreover, the maximum product yield in the C 2 OHMIM·NO 3 -containing system (95.2%) was not significant different with that of the C 4 MIM·PF 6 /buffer biphasic system (97.7%) [13] but much higher than that of the aqueous system (81.3%) [12]. The product e.e.…”

“…Under the optimized conditions described above, the initial reaction rate in the C 2 OHMIM·NO 3 -containing co-solvent system reached 17.3 µmol/h g cell , which was much faster than that in both aqueous monophasic system (14.5 µmol/h g cell ) [12] and the C 4 MIM·PF 6 -based IL/buffer biphasic system (5.5 µmol/h g cell ) [13]. Accordingly, the reaction time was greatly shortened from about 12 h to 1 h when replaced the IL/buffer biphasic system to the C 2 OHMIM·NO 3 -containing co-solvent system.…”

A Synergic Blend of Newly Isolated Pseudomonas mandelii KJLPB5 and [hmim]Br for Chemoselective 2° Aryl Alcohol Oxidation in H2O2: Synthesis of Aryl Ketone or Aldehydes via Sequential Dehydration-Oxidative C=C Cleavage

“…Ionic liquid ([hmim]Br) was synthesized according to reported method [31][32][33]. The solvents used for isolation/purification of compounds were obtained from Merck and used without further purification.…”

“…In continuation of our interest in the use of ionic liquids in biocatalytic synthesis and taking into account the encouraging results of our previous study on alcohol oxidation with lipase and [hmim]Br [21], we were interested to explore microbial catalyst from Western Himalayan region for metal free oxidative transformations, especially those involving user friendly reagent H 2 O 2 which generally requires metal activation [21]. Such whole cell transformations are preferable as they eliminate the need for enzyme purification and coenzyme addition/regeneration [31].…”

Asymmetric reduction of ketones with recombinant E. coli whole cells in neat substrates

“…To overcome substrate and product instability in aqueous media, either biphasic systems were applied, or the derivatized trimethylsilane-based compound was used as a substrate, albeit at the cost of adding further synthetic steps. [33][34][35]37 So far, alcohol dehydrogenases displayed low-to-moderate enantioselectivities in monophasic systems (5-86% [32][33][34][35] ), whereas the hydrolase-catalyzed ester hydrolysis led to high ee's, but with limited conversions at 50%. 38,39 To date, there is only one multi gram-scale preparation of (S)-3-butyn-2-ol using an alcohol dehydrogenase from Pseudomonas aeruginosa in a biphasic system with ee > 99%, though at low conversion (45.5%).…”